FIG. 8 is a perspective view of a traditional turning-fork piezoelectric vibrator, looking from a first side thereof. FIG. 9 is a perspective view of that piezoelectric vibrator, looking from a second side thereof. A piezoelectric vibrator 1 includes a turning fork vibrating body 2. The vibrating body 2 is constructed of two bonded tuning-fork piezoelectric substrates. These piezoelectric substrates are oppositely polarized in their thickness directions. Two driving electrodes 3a and 3b are formed on a first principal surface of the vibrating body 2. The driving electrodes 3a and 3b are formed separately in a width direction of each of two legs. The driving electrodes 3a and 3b formed on one of the two legs are connected to the driving electrodes 3a and 3b formed on the other of the two legs, respectively, at the base of the vibrating body 2. Two detecting electrodes 4a and 4b are formed on a second principal surface of the vibrating body 2. These detecting electrodes 4a and 4b are formed in the two legs of the vibrating body 2, respectively.
When the piezoelectric vibrator 1 is used as a vibratory gyroscope, an oscillation circuit is connected between the two driving electrodes 3a and 3b. This oscillation circuit causes the two legs of the vibrating body 2 to vibrate so as to open and close. At this time, the piezoelectric vibrator 1 is driven by self-excited vibration at that resonant frequency. The two detecting electrodes 4a and 4b are connected to a differential circuit. When, in the state where the two legs of the vibrating body 2 vibrate so as to open and close, the vibrating body 2 rotates about an axis perpendicular to the two legs thereof, the vibration direction of the legs is changed by the Coriolis force. Because of this, signals having opposite phases corresponding to the Coriolis force are output from the detecting electrodes 4a and 4b, and the difference of the output signals from the detecting electrodes 4a and 4b is output from the differential circuit. Accordingly, the use of measurement of a signal of the differential circuit can detect an angular velocity of rotation applied to the piezoelectric vibrator 1 (see Patent Document 1).
There also is a piezoelectric vibrator 5 illustrated in FIGS. 10(a) and 10(b). The piezoelectric vibrator 5 includes two legs 6a and 6b. Each of these legs 6a and 6b is constructed of a vibrating portion in which two elongated piezoelectric substrates are bonded. In each vibrating portion, the bonded piezoelectric substrates are polarized in the opposite thickness directions thereof. Two electrodes 7a and 7b and two electrodes 7c and 7d arranged separately in the width direction are formed on a first principal surface of the vibrating portion. The two legs 6a and 6b are arranged in parallel with each other, a base 8 is formed on a first end of a second principal surface of the legs 6a and 6b, and they are formed in the shape of a tuning fork as a whole. Further, an electrode 9 is formed on the second principal surface of the vibrating portion constituting the legs 6a and 6b so as to extend from the side surface of the base 8.
When the piezoelectric vibrator 5 is used as a vibratory gyroscope, an oscillation circuit is connected between the inwardly adjacent electrodes 7b and 7c of the adjacent legs 6a and 6b and the outwardly adjacent electrodes 7a and 7d thereof. The outer electrodes 7a and 7d are connected to a differential circuit. Thus, the oscillation circuit causes the legs 6a and 6b to vibrate so as to open and close, as in the case of the piezoelectric vibrator illustrated in FIGS. 8 and 9. When the piezoelectric vibrator 5 rotates about an axis parallel to the two legs 6a and 6b, the vibration direction of the legs 6a and 6b is changed by the Coriolis force, and a signal corresponding to the Coriolis force is output from the differential circuit. Accordingly, the use of measurement of a signal from the differential circuit can detect an angular velocity of rotation applied to the piezoelectric vibrator 5 (see Patent Document 2).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 10-111132
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-61486